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Allow user to customize additional variable names to be replaced by self with the strongifiedSelf rule #523

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Allow user to customize additional variable names to be replaced by self with the strongifiedSelf rule #523

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4826cfe
Add additional variable names to exclude from strongifiedSelf
krunk4ever Jan 3, 2020
a0c1360
Update rule info
krunk4ever Jan 3, 2020
7e3cb26
Update strongifiedSelf description
krunk4ever Jan 3, 2020
e12614b
Add test for strongSelf
krunk4ever Jan 3, 2020
28470e2
Add strongifiedSelfIdentifiers option
krunk4ever Jan 3, 2020
576a461
Use formatter options instead of hardcoding list
krunk4ever Jan 3, 2020
a99cba1
Add argument tests for strongifiedSelfIdentifiers
krunk4ever Jan 3, 2020
e3f5178
Update rules tests for when option is provided or missing for strongi…
krunk4ever Jan 3, 2020
5364008
Update test manifest
krunk4ever Jan 3, 2020
d42fcca
Make test names clearer
krunk4ever Jan 3, 2020
3fe0098
Update description for strongifiedSelf
krunk4ever Jan 3, 2020
225dc96
List strongifiedSelfIdentifiers in strongifiedSelf rule option
krunk4ever Jan 3, 2020
68131f1
Shorten strongifiedSelfIdentifiers to strongSelfIds
krunk4ever Jan 3, 2020
ad8294a
Update strongselfids description
krunk4ever Jan 3, 2020
54da3b2
Shorten description to max of 80 characters
krunk4ever Jan 3, 2020
099412d
Fix option name
krunk4ever Jan 3, 2020
d6a6258
Update help message for strongSelfIds to be the shortened version
krunk4ever Jan 3, 2020
a53b488
Update description
krunk4ever Jan 3, 2020
5c604df
Don't define output when it's the same as input
krunk4ever Jan 3, 2020
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18 changes: 10 additions & 8 deletions Sources/Rules.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -3758,20 +3758,22 @@ public struct _FormatRules {
}
}

/// Removed backticks from `self` when strongifying
/// Standardize on using self when strongifying self
public let strongifiedSelf = FormatRule(
help: "Remove backticks around `self` in Optional unwrap expressions."
help: "Standardize on using self when strongifying self."
) { formatter in
guard formatter.options.swiftVersion >= "4.2" else {
return
}
formatter.forEach(.identifier("`self`")) { i, _ in
guard let equalIndex = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: i, if: {
$0 == .operator("=", .infix)
}), formatter.next(.nonSpaceOrCommentOrLinebreak, after: equalIndex) == .identifier("self") else {
return
["`self`", "ss", "sSelf", "strongSelf"].forEach { idName in
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formatter.forEach(.identifier(idName)) { i, _ in
guard let equalIndex = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: i, if: {
$0 == .operator("=", .infix)
}), formatter.next(.nonSpaceOrCommentOrLinebreak, after: equalIndex) == .identifier("self") else {
return
}
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I don't think this will work. It only replaces the identifier if it appears in an expression like strongSelf = self, but it won't replace any references to strongSelf in the subsequent code.

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@krunk4ever krunk4ever Jan 3, 2020 •
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@nicklockwood, yeah, I also discussed this with my coworkers to see if autocorrect was the right thing to do here. there's actually 3 things that need to be autocorrected:

  1. Rename the disallowed variable name with self
  2. Update any references to the disallowed variable name to self
  3. Fix optionality of existing references to self which are no longer optional

Example for number 3:

{ [weak self] in 
  guard let strongSelf = self else { return }
  self?.doWork()
}

In the above example, we would also need to remove the trailing ? after self:

{ [weak self] in
  guard let self = self else { return }
  self.doWork()
}

(2) and (3) both feel really complicated for autocorrection w/o full understanding of the code graph and would be probably better off with human intervention. However, we still found it to be useful for autocorrect to complete step (1) despite the fact it might leave the code uncompilable.

thoughts?

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@nicklockwood nicklockwood Jan 4, 2020 •
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  1. is similar in complexity to what I already do for removing implicit self. It's certainly complicated because it requires an understanding of scope and tracking variable declarations and shadowing, but it's a local problem (i.e. it doesn't require knowledge of externally-defined symbols and their types) so it can be solved.

  2. is probably too difficult since modifications from optional to non-optional may be nontrivial, but I also think it's a bad idea generally because the developer may have a good reason for referencing self? rather than strongSelf and a formatter shouldn't second-guess that. However it wouldn't be hard to detect the user of self and not replace strongSelf in those cases.

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Just doing 1) and leaving code non-compilable is not acceptable IMO. Now that SwiftFormat has fairly decent linting capability, it might make sense to introduce the concept of "lint-only" rules for cases like this, where it would warn but not actually replace the symbol.

But TBH, it would probably make more sense to make it a SwiftLint rule instead in that case.

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Yeah, we have a simple SwiftLint custom rule for detecting this for now:

  reuse_self_for_strongified_self:
    name: Reuse self for strongified self
    regex: "(?i) (s|ss|sSelf|strongSelf) = self[\n ,]"
    message: "Reuse self as the variable name when strongifying self as per Airbnb Swift style guide"
    severity: error

If you have an idea of how to autocorrect for (2), that would be great! I can take a look at removing implicit self and see if I can mimic that behavior, but if you have pointers or have the bandwidth to add that, even better!

formatter.replaceToken(at: i, with: .identifier("self"))
}
formatter.replaceToken(at: i, with: .identifier("self"))
}
}

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